PURPOSE: To enhance the utilization efficiency of a beam by enlarging linearly the beam with a deflection electromagnt means based on the difference of energy for which a charged particle ray beam has, and also, executing a processing so as to equalize the energy enlarged by an equalizing means.

CONSTITUTION: This beam enlarging device 2 generates a linear beam 6 by enlarging linearly an incident thin beam 4, and is provided with an energy distribution generator 8, a deflection electromagnet 10 and an energy distribution correcting device 12. The energy distribution generator 8 is an element whose thickness is ununiform in accordance with a place, and when the charged particle ray (thin beam) 4 passes through, since its energy loss is different in accordance with a place, the energy distribution is formed in the charged particle ray 4. Also, in the deflection electromagnet 10, since the degree of being curved by energy for which the beam 4 has is different, a beam 14 enlarged linearly is obtained, and at the time of transmitting through the energy discribution correcting device 12, the energy distribution of the beam 4 becomes small.